The embodiments described herein relate generally to gas turbine engine rotors, and more specifically, to rotor blades and platforms used in gas turbine engine rotor assemblies.
At least some known gas turbine engines compress air via a plurality of rotatable compressor blades and ignite a fuel-air mixture in a combustor to generate combustion gases that are channeled through rotatable turbine buckets along a hot gas path. Rows of blades or buckets convert thermal energy in the combustion gas stream into mechanical energy that rotates a turbine shaft, which may be used to power a machine, for example, an electric generator, a compressor, or a pump.
The rows of blades, which may be located in either or both of a compressor section and a turbine section of the gas turbine engine, are typically fixed to a rotor disc, that is rotatable around a central axis of the gas turbine engine. At least some blades are secured to the rotor disc by inserting a dovetail base portion of the individual blades into a corresponding dovetail slot in the rotor disc. Moreover, at least some known rotor blades include an integral platform that extends from the blade between the dovetail and an airfoil portion. When the blades extend outward from the rotor disc, the platforms define an inner flow path of the compressor or turbine section.
Blade and platform designs are at least partially limited by stresses induced to the airfoil shape during gas turbine engine operation, and materials for the blade are thus chosen to withstand such stresses. The platform area is subjected to lower levels of stress, but because it is integral to the blade, it is generally fabricated rom of the same material. As a result, the platform area may be over-designed and may be more costly and/or heavier than necessary than in a one piece blade. Furthermore, known integral blades include complex geometries, such as cooling passages or flanges, within the blade portion and/or the platform portion that present difficulties during the forging of such blades and that generally increase the costs and time associated with the manufacturing process.